30-06 is a 30 cal bullet which should be 300 thou but is really 308 thousandths of an inch and is commonly designated a 7.62 mm NATO which it isn't because that's measured at the inside of the lands, so its actually 7.82mm.
7.62 NATO isn't the same thing as 30-06. 7.62 NATO refers to a specific cartridge, not the bullet projectile itself. It's the same as .308 Winchester. 7.62x51mm.
Not too get to off topic, but the wildest shit to me is that with a 308 I can buy 7.62 ammunition that was made by Greece during WW2 and recently discovered in a sealed bunker and just straight up shoot with it like no time has passed.